Conventional linkers for antibody-drug conjugates (ADCs) employ lysine- or cysteine-reactive chemistries for the attachment of drug to antibody, with the seminal cases being all of the current FDA-approved ADCs. A major drawback of these chemistries is that the sites and the extent of conjugation are variable, producing heterogeneous products that can have different pharmacokinetic and cytotoxic properties. To counteract this issue, advances have been made to apply bioorthogonal chemistries for the production of homogeneous ADCs. However, many of these chemistries are slow or require a large excess of linker-payload to reach maximal coverage of the conjugation sites. Here, we present the chemistry of 2-formylphenylboronic acid (2fPBA) coupling with hydrazides as novel linker chemistry for ADCs. We have recently reported that 2fPBA exhibits fast reaction kinetics with hydrazine- and hydrazide-containing molecules and forms a stable boron-nitrogen heterocyclic (BNH) product. We show herein that an antibody and a fluorophore (as payload) introduced with 2fPBA and hydrazide functionalities undergo rapid conjugation at near-stoichiometric ratios. The linkage is site-specific as demonstrated by SDS-PAGE and mass spectrometry. Stability of the BNH conjugate is also demonstrated in plasma. Altogether, our results show promise for utilizing 2fPBA-hydrazide chemistry as a facile conjugation strategy to achieve fast and efficient production of homogeneous ADCs.

Novel chemistry for site-specific antibody bioconjugates

256th National Meeting (2018)

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